JohnSt. Clair, Master of Sinclair was baptised on 5 December 1683.1 He was the son of HenrySt. Clair, 1st/10th Lord Sinclair and GrizelCockburn.2 He married, firstly, LadyMargaretStewart, daughter of JamesStewart, 5th Earl of Galloway and LadyCatherineMontgomerie, circa August 1733.1 He married, secondly, AmeliaMurray, daughter of Lt.-Gen. LordGeorgeMurray and AmeliaMurray, on 24 April 1750.1 He died on 2 November 1750 at age 66, without issue.1 He was styled as Master of Sinclair.1 In 1708 he killed two brothers called Schaw in affrays which were called duels, although no seconds were present, and was forced to resign from his regiment.1 He gained the rank of Captain-Lieutenant in 1708 in the Preston's Regiment.1 He held the office of Member of Parliament (M.P.) (Tory) for Dysart Burghs in 1708, however the election was pronounced invalid since he was eldest son of a peer.1 He fought in the Battle of Sheriffmuir on 13 November 1715, as a Jacobite.1 He was attainted and barred from succession to peerage, although pardoned by Letters Patent 1723 with further relief by a Private Act of Parliament in 1736.1 He wrote the book Memoirs of the Rebellion.1